About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Spotlight on Optics

January 2013

Spotlight Summary by Summer Gibbs

Combination of spectral and fluorescence imaging microscopy for wide-field in vivo analysis of microvessel blood supply and oxygenation

Abnormalities in tissue microvasculature and angiogenesis are characteristic of a wide variety of disease pathologies including diabetes, hypertension, and cancer. In normal tissue, tissue homeostasis is maintained through a steady blood supply, which has the dual purposes of providing adequate nutrients and removing byproducts from the tissue. In diseased tissues, such as cancer, microvessel formation is often irregular leaving some tissues with decreased blood flow that results in hypoxia. Methodologies to characterize tissue blood flow and oxygenation are necessary to further understand and characterize disease as well as study the effects of treatment strategies. Currently there are a number of imaging modalities to analyze tumor microvasculature in small animal models. Optical imaging is well suited to studying tissue blood oxygenation as hemoglobin absorption provides endogenous contrast. However, blood flow is more difficult to differentiate by optical imaging modalities, unless exogenous contrast is utilized.

In the current study by Lee et al., the authors use hyperspectral imaging to determine hemoglobin oxygenation status from the endogenous absorption spectra of blood within the microvessels. This technique is combined with administration of exogenous near infrared (NIR) fluorescent liposomes, termed first pass fluorescence (FPF) imaging, to detect the entrance of the NIR fluorophores into the microcirculation. FPF imaging provides information about blood flow, microvessel morphology, and microvessel network connections through measurement of the blood supply time within the field of view. These imaging modalities were used together to study the microvasculature development of human renal cell carcinoma tumors implanted in mouse dorsal skinfold window chamber models. Microvasculature development was monitored over a four-day time period following tumor implantation in the window chamber. Using both hyperspectal imaging and FPF imaging both the increased speed of blood flow and oxygenation status of the tumor tissue could be seen by the fourth day of imaging. This combined imaging technique also demonstrated insight into how vascular malformations such as ateriovenous shunts create an oxygenated environment in which an immature tumor can proliferate. Since this technique enables serial imaging over multiple days it may be useful for studying therapeutic methods to normalize diseased tissue vasculature in the future.

Article Reference

Combination of spectral and fluorescence imaging microscopy for wide-field in vivo analysis of microvessel blood supply and oxygenation